Anesthesia and analgesia
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Anesthesia and analgesia · Mar 2005
Dexmedetomidine decreases the convulsive potency of bupivacaine and levobupivacaine in rats: involvement of alpha2-adrenoceptor for controlling convulsions.
Dexmedetomidine, a highly selective alpha(2)-adrenoceptor agonist, is used in combination with local anesthetics for sedation and analgesia. We tested the hypothesis that dexmedetomidine used for sedation alters the convulsive potency of racemic bupivacaine and levobupivacaine in awake, spontaneously breathing rats. In the first experiments, male Sprague-Dawley rats were randomly divided into six groups: bupivacaine with no dexmedetomidine (bupivacaine control; BC), bupivacaine with small-dose dexmedetomidine (BS), bupivacaine with large-dose dexmedetomidine (BL), levobupivacaine with no dexmedetomidine (levobupivacaine control; LC), levobupivacaine with small-dose dexmedetomidine (LS), and levobupivacaine with large-dose dexmedetomidine (LL) (n = 10 for each group). ⋯ Convulsive doses and plasma and brain concentrations of bupivacaine and levobupivacaine at the onset of convulsions in rats receiving yohimbine and dexmedetomidine were significantly smaller than in those receiving only dexmedetomidine (P < 0.05 for all) and were similar to those without dexmedetomidine or yohimbine. We conclude that dexmedetomidine used for sedation decreases the convulsive potency of both bupivacaine and levobupivacaine in rats. Alpha(2)-adrenoceptor agonism may be involved in this anticonvulsant potency.
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Anesthesia and analgesia · Mar 2005
Sepsis stage dependently and differentially attenuates the effects of nondepolarizing neuromuscular blockers on the rat diaphragm in vitro.
We investigated the effects of early and late sepsis on the actions of nondepolarizing neuromuscular blockers by using a rat sepsis model induced by cecal ligation and puncture. Isometric twitch tensions of nerve-hemidiaphragm preparations elicited by indirect (phrenic nerve) supramaximal stimulation at 0.1 Hz were evaluated. Rocuronium, pancuronium, and d-tubocurarine dose-dependently decreased the twitch tensions of the nonseptic, early septic, and late septic diaphragms (P < 0.01 each by analysis of variance [ANOVA]). ⋯ The standardized rightward shifts in early and late sepsis were largest for pancuronium, second largest for rocuronium, and smallest for d-tubocurarine (5.741, 2.979, and 1.660 times in late sepsis, respectively; P < 0.01 each by ANOVA and the Scheffe F test). Sepsis-induced increases in IC(50) values did not accompany the decreases in slopes. The results indicate that sepsis induces hyposensitivities to nondepolarizing neuromuscular blockers, the degree of which depends on the stage of sepsis and on the kind of neuromuscular blocker.
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Anesthesia and analgesia · Mar 2005
Testing the reliability of a new ultrasonic cardiac output monitor, the USCOM, by using aortic flowprobes in anesthetized dogs.
We have used an animal model to test the reliability of a new portable continuous-wave Doppler ultrasonic cardiac output monitor, the USCOM. In six anesthetized dogs, cardiac output was measured with a high-precision transit time ultrasonic flowprobe placed on the ascending aorta. The dogs' cardiac output was increased with a dopamine infusion (0-15 microg x kg(-1) x min(-1)). ⋯ In five of six dogs, there was a high degree of concordance, or agreement, between the 2 methods, with coefficients >0.9. The USCOM provided reliable measurements of cardiac output over a wide range of values. Clinical trials are needed to validate the device in humans.
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Anesthesia and analgesia · Mar 2005
Editorial CommentGoldilocks: the pediatric anesthesiologist's dilemma.